Terms and conditions
Mileage Plan members who register for this promotion before their first
qualifying flight will receive double base miles on nonstop Japan
Airlines flights between Seattle (SEA), and Tokyo (NRT), for travel from
March 31, 2019, through May 31, 2019. Double miles are valid on fares booked in J, C, D, X, I, Y, B, H, K, M, L, V, S, N, Q, O classes of service . Percentage of base miles earned can be viewed on the Japan Airlines partner page.
Flights must be marketed and operated by Japan Airlines. Mileage for
qualifying flights must be credited to the member’s Mileage Plan
account. Double miles earned are based on the class of service flown.
The percentage earned can be viewed on the Japan Airlines partner page.
The offer is not valid on free or award travel. Double miles do not
count towards Mileage Plan elite status. Double miles will be awarded
within four to six weeks of meeting the promotion’s qualifications. All
terms and conditions of the Mileage Plan program apply. The offer is
subject to change without notice.

Note that you can also choose to earn Double JAL Mileage Bank miles on this flight, see here for details

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